System-in-Package Testing: Problems and Solutions
IEEE Design & Test
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Smart wireless sensor systems that incorporate multiple sensors often cannot be implemented on a single chip. Advanced integration and assembly allows for a more complex conjugation and configuration of multiple system modules implemented under different technologies together in a small tiny package. In tiny sensor systems such as these, three common challenges seen across most platforms are: the difficult test access due to non-standard assembly and packaging, the testing of multiple heterogeneous sensor species, and the strict dimensional requirements limiting availability of any built-in hardware for testing. We discuss the method of testing by modules for testing a multilayer mechanically flexible wireless multisensor platform. A hierarchical test flow is presented for verifying the functionalities and assessing the performance of the various modules of the system. We also present an example of a design for testing feature, a built-in test point access bus that improves reliability for test point access, reduces the cost of testing and overall system bill-of-material, as well, increases test channel bandwidth allowing for full access to all critical subsystem nodes. Lastly, we provide examples of subsystem performance assessment and verification testing of selected sensor species on the multisensor platform as well as the system power consumption versus transmission range, to illustrate the usefulness of the test concepts, flow, and features introduced.